1. Field of the Invention
The present invention relates to a novel pattern forming method and, more specifically, a method for forming a monomolecular film or a monomolecular built-up film on a base.
2. Description of the Prior Art
Until recently, inorganic substances, which are relatively easy to handle, have been exclusively used in semiconductor and optics technology. One reason might be that the technology of organic chemistry was far behind that of inorganic chemistry.
However, the technology in organic chemistry has strikingly progressed in recent years and, moreover, the development of the material composed of the inorganic substance seems to have slowed down. Therefore, a functional organic material surpassing the inorganic substances has been desired. The advantage of the organic material is low price, easy production, excellent functional properties and so on. Further, the organic materials have been developed recently which have superior heat-resistance and mechanical strength to those in the prior arts. With such a technical back ground, several reserach organizations presented recently the idea on utilizing organic thin film in place of the conventional inorganic thin film for a part or the whole of functional portion (principally thin layer portion) of an integrated circuit device including a logical element, a memory device, a photoelectric transducing device, etc. and of optical devices including microlens array, an optical wavepath, etc. They also presented the idea on preparing a molecular electron device by giving a function of a logic element, memory device or the like to an organic molecule, or on preparing a logic element comprised of bio-material (e.g. bio-chips).
A monomolecular built-up method (or Langmuir-Blodgett method) is known as a method for forming a thin film in fabrication of the above-mentioned various devices using the said organic material.
Langmuir-Blodgett method is a method for preparing a monomolecular film or a built-up film of monomolecular layer utilizing the phenomena in which a molecule having both hydrophilic and hydrophobic groups, when the balance of the both groups (hydrophilic and hydrophobic balance) is appropriate, forms a layer on the water surface with the hydrophilic group orienting downwards.
With this method, the formation of the monomolecular film or the monomolecular built-up film on the desired substrate is carried out generally by raising or lowering the substrate vertically through the water surface having the developed monomolecular film composed of a layer of the above-mentioned molecule. By using a single kind of molecule developed on the water surface, the monomolecular film or the monomolecular built-up film comprising the single kind of molecule may be formed. On the other hand, when two or more kinds of molecule dissolved in a vaporizable solvent is developed on the water surface, the mixed monomolecular film or the mixed monomolecular built-up film of a uniform constitution comprising two or more kinds of molecule may be formed by transferring the developed solution on the substrate.
For fabricating said various devices with the deposited monomolecular film or the monomelecular built-up film having various functions such as a photoconductivitity and the like, it is necessary to control a two-dimensional arrangement of the monomolecular film or the monomolecular built-up film. However, in the above method, the two-dimensional patterning could not be controlled because the monomolecular film or the monomolecular built-up film is formed on the whole surface of the substrate, except where a photoresist for a lithography using a special photopolymerization property is utilized, that is, except where the molecule constituting the monomolecular film or the monomolecular built-up film has a property of photoresist.